SkyEye

The upper chart shows the path of Mercury across the background stars over the course of the year. Stars to magnitude +4.5 are shown with some fainter objects included to complete constellation patterns. The white circles represent the planet on the first day of the month and are scaled according to apparent magnitude. The faint paths before the first circle and after the last circle represent the planet's positions in December of last year and January of next. In general, the planet moves from right to left except when it's in retrograde and proceding in the opposite direction. As an inferior planet, Mercury never strays far from the Sun so it always begins and ends the year near the constellation of Sagittarius, located about one quarter of the way in from the left side of the chart.

The lower charts show how the appearance of Mercury changes over the year. Below each image is listed the date, the apparent magnitude, the apparent diameter of the disk (in arc-seconds), the geocentric distance (in au), the elongation from the Sun (in degrees) and the percentage of the disk which is illuminated. Like the Moon, Mercury exhibits a complete range of phases, from new to crescent to gibbous to full and back again. Because its synodic period is around four months, Mercury completes this phase cycle three times each year. Note how Mercury's magnitude varies widely, ranging (approximately) from −2.0 to +6.0 between conjunctions.

The closest planet to the Sun is an elusive object to spot in the sky. It begins the year in the morning sky but is low to the horizon before sunrise and soon lost to view as it heads toward conjunction in February. The March apparition in the west is best seen from northern latitudes with the April apparition in the east favouring the southern hemisphere. Lost to view in June during superior conjunction, Mercury is again an evening sky object in July, this time favouring southern latitudes. Another conjunction in August brings the tiny planet back into the dawn sky for the best morning apparition this year for northern observers. Superior conjunction in late September is followed by good observing in the evening for those in southern latitudes. After the November conjunction, the northern hemisphere is again favoured for seeing Mercury in the morning sky before sunrise.

• Apparitions of the Inferior Planets from Latitude 50° North
• Apparitions of the Inferior Planets from Latitude 10° North
• Apparitions of the Inferior Planets from Latitude 30° South

Sources

The dates, times and circumstances of all planetary and lunar phenomena were calculated from the JPL DE406 solar system ephemeris using the same rigorous methods that are employed in the compilation of publications such as The Astronomical Almanac.